No description available.

Master of Science / Department of Chemistry / Kenneth J. Klabunde / Although Degussia-Huls P-25 TiO[subscript]2 semiconductor photocatalyst has high photodegradation rate for organic molecules, it works only under ultra-violet (UV) light. Mesoporous metal doped V-MCM-48 silica was synthesized under ambient conditions for use as a visible-light photocatalyst to convert toxic probe molecules to innocuous products: CO[subscript]2 + H[subscript]2O. The synthesis employed a modified Stober metal doped MCM-48 silica method. Powder X-ray diffraction (XRD), diffuse-reflectance-ultra-violet-visible (DR-UV-vis) spectroscopy, and N[subscript]2 adsorption-desorpton analysis characterization methods were completed on V-MCM-48 mesoporous material. These characterization methods indicate V-MCM-48 structure had formed with visible light absorption and mesoporous properties. Photocatalysis studies were completed with V-MCM-48 under dark, visible, and UV-light illumination conditions for the following probe molecules: acetaldehyde, carbon monoxide, ethanol, acetone, 2-propanol, and acetonitrile. Acetaldehyde over V-MCM-48 was converted to CO[subscript]2 under dark, visible, and UV-light conditions. Carbon monoxide photooxidation occurred over V-MCM-48 under visible and UV-light. Ethanol and acetonitrile had smaller photodegradation activity over V-MCM-48. Acetone and 2-propanol had no activity photocatalytically. Under dark and visible light illumination, V-MCM-48 consumed approximately one-half acetaldehyde and produced one-third CO[subscript]2 concentration as compared with the P-25 TiO[subscript]2 under UV-light. V-MCM-48 produced two-thirds of the amount of CO[subscript]2 in comparison to nanoparticle Au/ZnO catalyst under UV-light. The results infer V-MCM-48 might be useful in gas and liquid phase photocatalysis including water-splitting due to a high oxidation state (V[superscript]5+), visible light absorption, and high surface area. In conclusion, an extended literature review has been completed and literature employed extensively throughout the thesis with potential methods to further the research on V-MCM-48/Si-MCM-48 in catalysis, chromatography, adsorption/gas separation, and solar collection/water-splitting.

Le procédé sol-gel non-hydrolytique (SGNH) offre une alternative intéressante au procédés sol-gel classiques. Notamment, la « voie éther », impliquant la réaction de précurseurs chlorures ou oxychlorures avec avec un éther comme donneur d’oxygène, est une méthode simple et efficace pour la préparation d’oxydes et d’oxydes mixtes mésoporeux. Les batteries Li-ion sont omniprésentes aussi bien dans des applications portables que pour des véhicules électriques ou hybrides. Cependant, les performances des électrodes commerciales sont insuffisantes pour des applications haute puissance. TiO2 est un candidat prometteur pour remplacer les anodes de graphitie dans les batteries Li-ion, mais sa conductivité électronique doit être améliorée. L’objectif de ce travail de thèse est d’utiliser les avantages du procédé SGNH pour préparer des matériaux d’électrodes à base de TiO2. Deux approches ont été explorées, mettant en jeu la voie éther en l’absence de tout solvant ou additif. Premièrement, des oxydes mésoporeux à structure hiérarchique, TiO2 et TiO2-V2O5, ont été synthétisés par calcination des xérogels. Deuxièmement, des nanocomposites mésoporeux constitués de nanoparticules de TiO2 recouvertes d’un film de carbone ont été obtenus par pyrolyse sous atmosphère d’argon, l’éther jouant le rôle de donneur d’oxygène et aussi, pour la première fois, de source de carbone. Les matériaux ont été caractérisés par physisorption d’azote, microscopie électronique, DRX, spectroscopie Raman, ATG ainsi que par RMN 13C CPMAS pour les nanocomposites. Les performances en insertion-désinsertion du lithium ont été étudiées par cyclage galvanostatique à différentes densités de courant. / Non-hydrolytic sol-gel (NHSG) provides useful alternatives to conventional sol-gel routes. In particular, the ether route based on the reaction of chloride or oxychloride precursors with ether oxygen donors is a well-established method for the preparation of mesoporous oxides and mixed-oxides. Li-ion batteries are ubiquitous in the field of electrochemical energy storage, from mobile devices to electric and hybrid vehicles. However, commercial electrode materials do not fulfill all the requirements needed for high-power applications. TiO2 is as a promising material to replace graphite anodes in high-power Li-ion batteries, despite its poor electronic conductivity, which must be improved. In this context, the objective of this PhD thesis is the conception of different TiO2-based electrode materials benefitting from NHSG advantages. Two different approaches were developed, using the ether route in the absence of any solvent or additive. First, hierarchical mesoporous oxides, TiO2 and TiO2-V2O5, were synthesized by calcination of xerogels in air. Secondly, mesoporous nanocomposites built of carbon-coated TiO2 nanoparticles were obtained by pyrolysis under argon of the xerogels; in this case, the ether is used for the first time as both as an oxygen donor and a carbon source. The texture and the structure of the resulting materials were characterized by N2 physisorption, electron microscopy, XRD, and Raman spectroscopy. TiO2/C samples were further analyzed by TGA and 13C CPMAS-NMR. Galvanostatic cycling at different current rates was performed to determine the electrochemical performances in lithium insertion-deinsertion.

Made available in DSpace on 2014-12-17T15:41:47Z (GMT). No. of bitstreams: 1 KesiaKV.pdf: 2272602 bytes, checksum: 46f23a52fbc9d4e74dfd9f25d2f58e11 (MD5) Previous issue date: 2009-02-19 / In present work, mesoporous materials of the M41S family were synthesized, which were discovered in the early 90s by researchers from Mobil Oil Corporation, thus allowing new perspectives in the field of catalysis. One of the most important members of this family is the MCM-41, which has a hexagonal array of mesopores with pore diameters ranging from 2 to 10 nm and a high surface area, enabling it to become very promising for the use as a catalyst in the refining of oil in the catalytic cracking process, since the mesopores facilitate the access of large hydrocarbon molecules, thereby increasing the production of light products, that are in high demand in the market. The addition of aluminum in the structure of MCM-41 increases the acidity of the material, making it more beneficial for application in the petrochemical industry. The mesoporous materials MCM-41 and Al-MCM-41 (ratio Si / Al = 50) were synthesized through the hydrothermal method, starting with silica gel, NaOH and distilled water. CTMABr was used as template, for structural guiding. In Al-MCM-41 the same reactants were used, with the adding of pseudoboehmite (as a source of aluminum) in the synthesis gel. The syntheses were carried out over a period of four days with a daily adjustment of pH. The optimum conditions of calcination for the removal of the organic template (CTMABr) were discovered through TG / DTG and also through analysis by XRD, FTIR and Nitrogen Adsorption. It was found that both the method of hydrothermal synthesis and calcination conditions of the studies based on TG were promising for the production of mesoporous materials with a high degree of hexagonal array. The acidic properties of the materials were determined by desorption of n-butylamine via thermogravimetry. One proved that the addition of aluminum in the structure of MCM-41 promoted an increase in the acidity of the catalyst. To check the catalytic activity of these materials, a sample of Atmospheric Residue (RAT) that is derived from atmospheric distillation of oil from the Pole of Guamar?- RN was used. This sample was previously characterized by various techniques such as Thermogravimetry, FTIR and XRF, where through thermal analysis of a comparative study between the thermal degradation of the RAT, the RAT pyrolysis + MCM-41 and RAT + Al- MCM-41. It was found that the Al-MCM-41 was most satisfactory in the promotion of a catalytic effect on the pyrolysis of the RAT, as the cracking of heavy products in the waste occurred at temperatures lower than those observed for the pyrolysis with MCM-41, and thereby also decreasing the energy of activation for the process and increasing the rates of conversion of residue into lighter products / No presente trabalho, foram sintetizados materiais mesoporos da fam?lia M41S que foram descobertos no in?cio dos anos 90 por pesquisadores da Mobil Oil Corporation, possibilitando assim novas perspectivas no ramo da cat?lise. Um dos mais importantes membros desta fam?lia ? o MCM-41, que possui um arranjo hexagonal de mesoporos com di?metros de poros entre 2 a 10 nm e uma alta ?rea superficial, tornando-o bastante promissor para ser utilizado como catalisador no refino do petr?leo para o craqueamento catal?tico, j? que seus mesoporos facilitam o acesso de mol?culas grandes de hidrocarbonetos, aumentando assim a produ??o de produtos leves com uma alta demanda no mercado. A adi??o de alum?nio na estrutura do MCM-41 aumenta a acidez do material, tornando-o mais positivo para aplica??o na ind?stria petroqu?mica. Os materiais mesoporosos do tipo MCM-41 e Al-MCM- 41 (raz?o Si/Al=50) foram sintetizados atrav?s do m?todo hidrot?rmico partindo da S?lica gel, NaOH e ?gua destilada. Como direcionador estrutural foi utilizado CTMABr. Para o Al- MCM-41 utilizaram-se os mesmos reagentes acrescentando a pseudobohemita (fonte de alum?nio) no gel de s?ntese. As s?nteses foram realizadas durante um per?odo de quatro dias com corre??o di?ria de pH. As melhores condi??es de calcina??o para remo??o do direcionador org?nico (CTMABr) foram otimizadas por TG/DTG e atrav?s de an?lises por DRX, FTIR e adsor??o de nitrog?nio verificou-se que tanto o m?todo de s?ntese hidrot?rmica como as condi??es de calcina??o baseado nos estudos por TG foram promissores para produ??o de materiais mesoporosos com alto grau de ordena??o hexagonal. As propriedades ?cidas dos materiais foram determinadas pela dessor??o de n- butilamina via termogravimetria. Comprovou-se que a adi??o de alum?nio na estrutura do MCM-41 promoveu um aumento na acidez deste catalisador. Para verificar a atividade catal?tica desses materiais utilizou-se uma amostra do Res?duo Atmosf?rico (RAT) que ? proveniente da destila??o atmosf?rica do petr?leo proveniente do P?lo de Guamar?- RN previamente caracterizado por v?rias t?cnicas como: Termogravimetria, FTIR e FRX, realizando-se atrav?s da an?lise t?rmica um estudo comparativo entre a degrada??o t?rmica do RAT, pir?lise do RAT+MCM-41 e RAT+Al-MCM-41. Verificou-se que o Al-MCM-41 promoveu um efeito catal?tico mais satisfat?rio na pir?lise do RAT, j? que o craqueamento dos produtos pesados presentes no res?duo ocorreu em temperaturas inferiores ?s observadas para a pir?lise com MCM-41 e com isso diminuindo tamb?m a energia de ativa??o para o processo, bem como aumentando os valores de convers?o do res?duo em produtos leves

Les proazaphosphatranes sont des entités phosphorées bicycliques superbasiques également connues sous le nom de superbases de Verkade et les azaphosphatranes constituent leurs acides conjugués. Les travaux de cette thèse porte sur l’étude des propriétés de ces molécules en milieu confiné. Premièrement, le confinement des superbases a été étudié au sein de structure de type hémicryptophane (molécules possédant des cavités dissymétriques formées à partir d’une unité cyclotrivératrylène et d’une seconde unité de symétrie C3). Une modulation de la basicité a pu être notamment observée dans les différentes structures étudiées possédant des tailles de cavité différentes par comparaison avec les superbases modèles dépourvues de cavité. L’activité catalytique d’une superbase encagée a pu être testée dans deux réactions de catalyse nucléophile et basique. Puis les azaphosphatranes, acides faibles aux stuctures robustes, jusque-là peu utilisés en organocatalyse ont été valorisés pour la synthèse de carbonates cycliques à partir d’époxydes et de dioxyde de carbone (CO2). Un effet sur la stabilité des catalyseurs encagés a pu être démontré. Enfin un catalyseur hétérogène a pu être mis au point par immobilisation d’un azaphosphatrane sur silice mésoporeuse de type SBA-15. / Proazaphosphatranes are highly reactive phosphorous bicyclic compounds also called Verkade’s superbases and the azaphosphatranes are their acidic counterparts. The goal of the work is to investigate the modifications of the properties of these compounds when they are in confined space. Firstly, the superbases were encapsulated into hemicryptophane host compounds (molecular containers created from the association of a cyclotriveratrylene unit with another C3-symmetric moiety). Modifications in the basicity of the supramolecular superbases depending on the substitution pattern around the phosphorous were evidenced compare to the molecules lacking the cavity. The catalytic activity of a superbase was investigated on a nucleophilic and a basic reaction. The azaphosphatranes were then used to catalyze the cycloaddition of carbon dioxide (CO2) to epoxides to form a cyclic carbonate. Enhancements of the stability of encaged catalyst were demonstrated. Finally, an azaphophatrane was immobilized on mesoporous silica leading to a heterogeneous catalyst.

No description available.

Nous avons étudié la conductivité thermique de particules de silice mésoporeuse organisée de type SBA-15 de morphologie bâtonnet et présentant trois états d’agrégation : non agrégées (morphologie A), agrégées en macrostructures fibreuses homogènes en taille (morphologie B) et agrégées en macrostructures fibreuses hétérogènes en taille (morphologie C). Ces trois types de morphologie ont subi un traitement thermique post-synthèse à des températures variables allant de 150 °C jusqu’à 900 °C. Les mesures de conductivité thermique ont été effectuées sur ces trois morphologies. Il s’est avéré que la morphologie B est la plus isolante par rapport aux deux autres morphologies. De plus, le traitement thermique post-synthèse à 300 °C est optimal pour avoir des caractéristiques texturales très importantes, ainsi qu’une meilleure performance en isolation thermique (23 mW.m-1.K-1 pour la poudre, 30 mW.m-1.K-1 pour le monolithe). Dans le cas de la morphologie B, nous avons modifié l’interconnexion entre les mésopores cylindriques réguliers qui caractérisent la SBA-15; soit la présence ou non de microporosité, voire de mésoporosité, en variant la température de l’étape de synthèse dite de vieillissement de 36 à 130 °C. Il apparait que la température de vieillissement à 130 °C améliore la performance d’isolation thermique (22 mW.m-1.K-1). Des pastilles de la SBA-15 de morphologie B en été élaborées par ajout de liants de deux types : organique avec la carboxyméthylcellulose, et inorganique avec une silice colloïdale. En ajoutant ces deux types de liants, les propriétés mécaniques sont un peu améliorées, cependant la performance d’isolation thermique diminue notablement. / We have studied the thermal conductivity of rod-shaped particles of ordered mesoporous silica (OMS) SBA-15 type with three states of aggregation: non aggregated (morphology A), aggregated in fibrous macrostructures homogeneous in size (morphology B) and aggregated in fibrous macrostructures heterogeneous in size (morphology C). These three types of morphology were heat treated at temperatures from 150 °C to 900 °C. The thermal conductivity measurements were performed on these three morphologies in powder form or monoliths (assembly of particles or aggregates). It has been found that the morphology B is more insulating compared to the two other morphologies. In addition, the post-synthesis heat treatment at 300 °C is optimum for obtaining important textural characteristics (specific surface area and pore volume), and a better thermal insulation performance (23 mW.m-1 K-1. for the powder and 30 mW.m-1.K-1 for the monolith). For morphology B, we have changed the interconnection between regular cylindrical mesopores of SBA-15 by varying the synthesis temperature during the aging step from 36 to 130 °C. It appears that the aging temperature at 130 °C, where the connection between the cylindrical mesopores is realized by mesopores, improves the performance of thermal insulation (22 mW.m-1.K-1). Monoliths of OMS SBA-15 type with morphology B were prepared by adding two kinds of binders: organic with carboxymethylcellulose (CMC), and inorganic with a colloidal silica (Ludox AS40). By adding these two kinds of binders, the mechanical properties of the SBA-15 with morphology B are improved, but the thermal insulation performance decreases considerably.

D. Tech. Chemical Engineering / Aims of this research project was to add value to largely wasted South African sawdust by development of low-cost AC of high efficiency for removal of toxic Cr (VI), phenol and glutaraldehyde from dilute aqueous media. The main objectives of the research project were: a) To develop low-cost AC based on South African P. patula sawdust using economical physical superheated steam activation.Characterization of carbon samples for selection of optimum preparation conditions for development of low-cost AC of effective microporosity mesoporosity and surface functionality for enhanced adsorption capacity of Cr (VI) and/or phenol and/or glutaraldehyde from dilute aqueous solution. Acid-amine surface groups modification of optimally developed AC for further enhancement of adsorption capacity for mixed polarized glutaraldehyde molecules from aqueous solution. b) To evaluate the aqueous phase batch adsorption properties of developed AC for Cr (VI) and phenol and, of acid-amine modified developed AC for glutaraldehyde. Determination of optimum pH for adsorption; accurate adsorption isotherm modelling for determination of maximum adsorption capacity, comparison of maximum adsorption capacities for Cr (VI) and phenol of developed AC with commercial AC and literature ACs, and attempt to establish average micropore size for enhanced capacity for Cr (VI) and phenol from dilute aqueous solution.Kinetics reaction and diffusion modelling for determination of adsorption rate constants and diffusion parameters; and determination of adsorption thermodynamic parameters.Evaluation of equilibrium selectivity of developed AC for Cr (VI) and/or phenol in binary aqueous solutions. c) To evaluate aqueous phase fixed-bed adsorption characteristics of developed AC for single Cr (VI) and mixed solution using Rapid Small Scale column Tests (RSSCTs). Generation of breakthrough curves at optimum adsorption conditions for evaluation of column performance indicators at different process conditions, bed regeneration-reusability potential, and dynamic adsorption selectivity of developed AC for Cr (VI) from solution of base metals. Determination of column diffusion parameters; accurate mass transfer and empirical modelling of breakthrough data; determination of applicable RSSCT scaling equation; and optimization of breakthrough data for accurate RSSCT scale-up.

Tesis por compendio / [ES] La funcionalización de partículas de sílice con componentes de aceites esenciales (EOCs) se ha propuesto como una estrategia prometedora para mejorar la actividad antimicrobiana y la estabilidad de estos compuestos. Sin embargo, debido a la potencial aplicación de estas partículas en la industria alimentaria, es necesario llevar a cabo estudios toxicológicos que permitan identificar los posibles efectos sobre la salud que puede conllevar el uso de estos nuevos materiales. En esta tesis doctoral, se ha evaluado el riesgo derivado de la exposición oral a tres tipos de partículas de sílice (SAS, micropartículas MCM-41 y nanopartículas MCM-41) funcionalizadas con cuatro tipos de EOCs diferentes (carvacrol, eugenol, timol y vainillina) y se ha comparado con el efecto de los EOCs libres y las partículas sin funcionalizar. La evaluación toxicológica de estos nuevos materiales se llevó a cabo a través de una estrategia formada por 3 tipos de estudios diferentes como son la simulación de condiciones fisiológicas, el uso de la línea celular HepG2 y el organismo modelo Caenorhabditis elegans. El primer paso en la evaluación toxicológica de las partículas consistió en estudiar su estabilidad en fluidos fisiológicos que simulan las condiciones de exposición por vía oral. Los resultados mostraron que la funcionalización con EOCs aumenta la biodurabilidad de las partículas en condiciones que representan el tracto gastrointestinal humano y el fluido lisosomal, como se observa tanto por la menor disolución de los diferentes tipos de partículas funcionalizadas como por la conservación de la estructura de las nanopartículas MCM-41. Sin embargo, el estado de aglomeración de las partículas no cambió en condiciones fisiológicas, y todas ellas se mantuvieron dentro del rango de tamaño de las micropartículas. Por tanto, dado su gran tamaño, estos materiales presentan un bajo riesgo de acumulación tras ingestión oral. El estudio in vitro de la toxicidad de los materiales demostró que las partículas funcionalizadas con EOCs presentan un efecto citotóxico mayor que los EOCs libres y la sílice sin funcionalizar. Además, independientemente del tipo de EOC, las micropartículas MCM-41 funcionalizadas fueron los materiales más citotóxicos. Los resultados sugieren que las partículas funcionalizadas con EOCs inducen toxicidad en las células HepG2 mediante un mecanismo relacionado con el estrés oxidativo, el cual provoca daño mitocondrial y la consecuente activación de procesos de apoptosis. Por otra parte, se demostró que este efecto citotóxico está causado por interacciones directas entre las células y las partículas, y no por productos de degradación liberados al medio de cultivo. La exposición aguda a concentraciones moderadas y altas de EOCs redujo la viabilidad de las células HepG2 y la supervivencia de C. elegans. La jerarquía de la toxicidad se mantuvo entre células y nemátodos, siendo el carvacrol el compuesto más tóxico, seguido del timol, el eugenol y, por último, la vainillina. Además, concentraciones subletales de estos componentes indujeron toxicidad reproductiva en C. elegans, lo que sugiere que pueden presentar efectos tóxicos a las concentraciones requeridas por sus propiedades bioactivas. El estudio in vivo de la toxicidad de las partículas mostró que tanto las partículas sin funcionalizar como las funcionalizadas con eugenol causan toxicidad reproductiva en C. elegans tras la exposición aguda, e inhibición en el crecimiento y la reproducción de los nematodos tras la exposición a largo plazo. Las partículas funcionalizadas con vainillina mostraron efectos tóxicos agudos leves, pero un mayor efecto tras la exposición a largo plazo. En líneas generales, los resultados obtenidos muestran que las partículas funcionalizadas con eugenol utilizadas en el estudio presentan mayores efectos sobre C. elegans que la sílice sin funcionalizar y las partículas funcionalizadas con vainillina. / [CA] La funcionalització de partícules de sílice amb components d'olis essencials (EOCs) s'ha proposat com una estratègia prometedora per a millorar l'activitat antimicrobiana i l'estabilitat d'aquests compostos. No obstant això, a causa de la potencial aplicació d'aquestes partícules en la indústria alimentària, és necessari dur a terme estudis toxicològics que permeten identificar els possibles efectes sobre la salut que pot comportar l'ús d'aquests nous materials. En aquesta tesi doctoral, s'ha avaluat el risc derivat de l'exposició oral a tres tipus de partícules de sílice (SAS, micropartícules MCM-41 i nanopartícules MCM-41) funcionalitzades amb quatre tipus de EOCs diferents (carvacrol, eugenol,timol i vanil·lina) i s'ha comparat amb l'efecte dels EOCs lliures i les partícules sense funcionalitzar. L'avaluació toxicològica d'aquests nous materials es va dur a terme a través d'una estratègia formada per 3 tipus d'estudis diferents com són la simulació de condicions fisiològiques, l'ús de la línia cel·lular HepG2 i l'organisme model Caenorhabditis elegans. El primer pas en l'avaluació toxicològica de les partícules va consistir a estudiar la seua estabilitat en fluids fisiològics que simulen les condicions d'exposició per via oral. Els resultats van mostrar que la funcionalització amb EOCs augmenta la biodurabilidad de les partícules en condicions que representen el tracte gastrointestinal humà i el fluid lisosomal, com s'observa tant per la menor dissolució dels diferents tipus de partícules funcionalitzades com per la conservació de l'estructura de les nanopartícules MCM-41. No obstant això, l'estat d'aglomeració de les partícules no va canviar en condicions fisiològiques, i totes elles es van mantindre dins del rang de grandària de les micropartícules. Per tant, donat la seua gran grandària, aquests materials presenten un baix risc d'acumulació rere ingestió oral. L'estudi in vitro de la toxicitat dels materials va demostrar que les partícules funcionalitzades amb EOCs presenten un efecte citotòxic major que els EOCs lliures i la sílice sense funcionalitzar. A més, independentment del tipus d'EOC, les micropartícules MCM-41 funcionalitzades van ser els materials més citotòxics. Els resultats suggereixen que les partícules funcionalitzades amb EOCs indueixen toxicitat en les cèl·lules HepG2 mitjançant un mecanisme relacionat amb l'estrés oxidatiu, el qual provoca dany mitocondrial i la conseqüent activació de processos d'apoptosis. D'altra banda, es va demostrar que aquest efecte citotòxic és causat per interaccions directes entre les cèl·lules i les partícules, i no per productes de degradació alliberats al mitjà de cultiu. L'exposició aguda a concentracions moderades i altes de EOCs va reduir la viabilitat de les cèl·lules HepG2 i la supervivència de C. elegans. La jerarquia de la toxicitat es va mantindre entre cèl·lules i nemàtodes, sent el carvacrol el compost més tòxic, seguit del timol, el eugenol i, finalment, la vanil·lina. A més, concentracions subletals d'aquests components van induir toxicitat reproductiva en C. elegans, la qual cosa suggereix que poden presentar efectes tòxics a les concentracions requerides per les seues propietats bioactives. L'estudi in vivo de la toxicitat de les partícules va mostrar que tant les partícules sense funcionalitzar com les funcionalitzades amb eugenol causen toxicitat reproductiva en C. elegans després de l'exposició aguda, i inhibició en el creixement i la reproducció dels nematodes després de l'exposició a llarg termini. Les partícules funcionalitzades amb vanil·lina van mostrar efectes tòxics aguts lleus, però un major efecte després de l'exposició a llarg termini. En línies generals, els resultats obtinguts mostren que les partícules funcionalitzades amb eugenol utilitzades en l'estudi presenten majors efectes sobre C. elegans que la sílice sense funcionalitzar i les partícules funcionalitzades amb vanil·lina. / [EN] Functionalisation of silica particles with essential oils components (EOCs) has emerged as a useful tool for enhancing EOCs' antimicrobial activity and stability. Given these new materials' promising applications for the food industry, toxicological studies must be performed to identify possible hazards for human health. In the present doctoral thesis, the potential risk deriving from oral exposure to three types of silica particles (SAS, MCM-41 microparticles, MCM-41 nanoparticles) functionalised with four different EOCs (carvacrol, eugenol, thymol, vanillin) was investigated and compared to free EOCs and pristine particles. For this purpose, three different replacement methods were used as a strategy to carry out the toxicological assessment of these new materials: simulated physiological conditions, HepG2 culture cells and the non-mammalian organism model Caenorhabditis elegans. As the expected human exposure to these materials was the oral route, the first step in the toxicological assessment of the silica particles was to study their degradation behaviour in acellular physiological fluids that mimic oral exposure conditions. The results showed that functionalisation of silica with EOCs increases particles' biodurability under conditions representing the human gastrointestinal tract and lysosomal fluid, as observed by both, the lower dissolution rates in the different functionalised particle types and the preservation of the EOCs-functionalised MCM-41 nanoparticles structure. However, the agglomeration state of the particles did not change under the physiological conditions, which remained within the micro-sized range in all cases. Therefore, given their large size, these materials present a low risk of accumulation after oral ingestion. The in vitro toxicity study showed that EOCs-functionalised particles displayed stronger cytotoxic effect than the free EOCs and pristine silica. Independently of EOC type, the EOCs-functionalised MCM-41 microparticles were the most cytotoxic materials from the different silica particle types analysed. Our results suggest that the EOCs-functionalised particles induce toxicity on HepG2 cells by an oxidative stress-related mechanism that causes mitochondrial dysfunction and apoptosis activation via the mitochondrial pathway. This cytotoxic effect was caused by direct cell-particle interactions, and not by degradation products released to culture media. Acute exposure to moderate and high concentrations of EOCs reduced HepG2 viability and nematode survival. The toxicity ranking was maintained between culture cells and nematodes, being carvacrol the most toxic compound followed by thymol, eugenol, and lastly by vanillin. Moreover, sublethal concentrations to these components induced reproductive toxicity in C. elegans, which suggests that they may present toxic effects at the concentrations required for their bioactive properties. The in vivo toxicity study of the particles showed that both the bare and EOCs-functionalised particles cause acute reproductive toxicity and inhibition in nematode growth and reproduction after long-term exposure. The vanillin-functionalised particles displayed milder acute toxic effects, but severer long-term exposure toxicological responses. However, the eugenol-functionalised particles exhibited stronger effects than the bare and vanillin-functionalised silica. / The authors gratefully acknowledge the financial support from the Spanish government (Project RTI2018-101599-B-C21 (MCUI/AEI/FEDER, EU)). Cristina Fuentes also thanks the Generalitat Valenciana for being funded by the predoctoral programme Vali+d (ACIF/2016/139). María Ruiz-Rico acknowledges the Generalitat Valenciana for her Postdoctoral Fellowship (APOSTD/2019/118). / Fuentes López, C. (2022). Toxicological assessment of silica particles functionalised with essential oil components and their constituents [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/181634 / TESIS / Compendio

Ce travail de thèse porte sur l’élaboration de matériaux siliciques mésostructurés par des agents structurants originaux : les micelles complexes de polyions ou micelles PICs, qui présentent la particularité de s’assembler de façon réversible dans l’eau. Les micelles PICs sont des assemblages formés par interactions électrostatiques entre un copolymère à blocs double-hydrophiles (DHBC) neutre-ionisable et un agent de micellisation de charge opposée au DHBC. Le DHBC utilisé est un poly(oxyde d’éthylène)-b-poly(acide acrylique) POE-b-PAA synthétisé par polymérisation radicalaire contrôlée par transfert d’atome (ATRP) et les agents de micellisation sont commerciaux (oligochitosane OC, antibiotiques aminoglycosides). Tout d’abord, l’influence de divers paramètres (pH, température, concentration) sur les propriétés d’association des micelles PIC a été étudiée en solution aqueuse. Puis, l’influence de ces mêmes paramètres sur la structuration de la silice en présence de complexes de polyions POE-b-PAA/OC a été recherchée, et a permis de mieux appréhender les mécanismes de formation des matériaux hybrides. Il a ainsi été montré qu’en jouant sur les interactions entre les divers constituants, il était possible de contrôler la mésostructure des matériaux (hexagonale, lamellaire, vermiculaire) et leur morphologie (nanoparticules, microparticules). Enfin, la versatilité de l’utilisation de micelles PIC en tant qu’agents structurants de la silice a été mise en évidence avec des systèmes POE-b-PAA/aminoglycosides, qui ont permis d’obtenir directement des matériaux structurés ordonnés chargés en principes actifs. Par ailleurs, les possibilités offertes par l’utilisation des micelles PIC notamment en termes de fonctionnalité et de réversibilité de la micellisation, ont été exploitées et ont permis d’obtenir facilement des matériaux mésoporeux fonctionnalisés par les chaînes ionisables du DHBC, suite à l’extraction sélective de l’agent de micellisation. Il a été montré que de tels matériaux fonctionnels sont capables de complexer des espèces de charges opposées et notamment des principes actifs, qui peuvent par la suite être relargués de façon pH-dépendante. / Mesostructured hybrid materials were prepared by using original silica-structuring agents, which are polyion complex (PIC) micelles. A great advantage of PIC micelles is that they can be reversibly assembled in aqueous solution by varying physico-chemical parameters. PIC micelles are formed by electrostatic complexation between a neutral-anionic double-hydrophilic block copolymer (DHBC) and an oppositely charged agent of micellization; here a poly(ethylene oxide)-b-poly(acrylic acid) PEO-b-PAA (synthesized by controlled radical polymerization by atom transfer ATRP) and commercial polyamines (oligochitosan OC or aminoglycoside antibiotics) were respectively used. First, the influence of various parameters (pH, temperature, concentration) on PIC micelle association properties was investigated in aqueous solution. Then, the effect of these parameters on the silica mesostructuring process was studied, it provides a better understanding of the formation mechanisms. It was shown that varying interactions between constituents allows to control the mesostructure (hexagonal, lamellar, wormlike) and the material morphology (nanoparticle, microparticle). Finally, the versatility of the approach has been demonstrated with PEO-b-PAA/aminoglycoside systems. Drug-loaded ordered mesostructured materials were prepared following a one-pot route. Moreover, taking advantage of the high degree of functionality of DHBC polymers and of the reversibility of the micellization, polyacid-functionalized mesoporous materials were directly prepared by selectively extracting the micellization agent. PAA-functionalized silica materials were then used to complex diverse active entities such as drugs, whose delivery could be pH-controlled.